This application claims the priority of German application 198 24 421.5, filed in Germany on May 30, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a casing construction on a gas turbine having a fan downstream of which a precompressor is situated. The precompressor casing is detachably connected with the casing of the compressor which follows the precompressor--viewed in the flow direction. Such a casing construction is conventional art, for example, in the case of flight gas turbines, that is, twin-jet engines, in which the precompressor is also called a booster.
It is also customary to provide safety measures which, in the case of a breakage--which although improbable, is nevertheless theoretically possible--of the shaft (in the following called a fan shaft), which is assigned to the fan as well as to the precompressor (or booster), prevent a movement of the fan (that is, of the fan disk with the blades) toward the front out of the jet engine.
A first safety measure of this type consists of constructing the fan shaft in such a massive construction that, as proven, no breakage can occur.
According to another safety measure, in addition to the fan shaft, another (redundant) safety shaft is provided which, in the event of a breakage of the former shaft, can take over all occurring loads.
Finally, it may be provided as a further safety measure that, in the event of a shaft breakage, any connection parts of the fan shaft, specifically, in particular, the precompressor rotor (or booster rotor), strike against stationary casing parts so that, as a result, the fan, including the broken shaft piece, is prevented from moving out of the jet engine casing. These stationary casing parts are then components of the casing of the precompressor (that is, the booster casing). In a concrete embodiment, in the event of a breaking of the fan shaft, the booster rotor would then strike against the inner ring of the initial guide blades of the booster (or precompressor) and would therefore be prevented by it from moving away.
So that the casing of the precompressor which is adjoined by the casing of the compressor which follows the precompressor, viewed in the engine flow direction, can carry out this described safety function, this precompressor casing, in turn, must have a correspondingly massive construction. The reason is that, after the precompressor casing has been fastened by means of its downstream end on the compressor casing, while the forces occurring during a breakage of the fan shaft have to be absorbed by the upstream end section of the precompressor casing (specifically as closely as possible to the fan), the precompressor casing must be designed for this (at least theoretically occurring) additional tensile load. Because of the required massive design, this leads not only to a high weight but, in addition, necessitates the use of high-strength materials for the booster casing, both of which is undesirable.
It is an object of the present invention to provide a remedial measure for the described problems.
This object is achieved in that the upstream end section of the precompressor casing is, in addition, linked to the compressor casing by means of at least two tension-rod-type tension devices which are situated essentially diametrically opposite one another with respect to the longitudinal axis of the gas turbine. Advantageous developments and further developments are described and claimed herein. In certain preferred embodiments, the tension-rod-type tension devices are constructed as steel cables.